Japanese printer company Brother has invented a battery that can be recharged by shaking it. It's intended for devices like remote controls that use very little power and would normally require infrequent battery charges, so unfortunately you couldn't use it to power a car that could drive forever on a bumpy road.

Energy is always lost when something is using it, usually converted to heat. A perfect system would be a perpetual motion machine, but that is impossible.

However, you can create systems that recycle as much of the energy as possible. For example, when we are walking, all of the energy we expend is lost. A system in our shoes that converts pressure to electricity (piezoelectricity it is called) can recharge our iPods or mobile phones.

Also the same technique can be used in roads specially constructed to create electricity when a moving car passes over them. Such a project is already being used experimentally.